Our body needs a constant flow of oxygen coming in so that cells can produce energy. Oxygen is delivered to cells via blood flow, and metabolic reactions that produce energy also create some waste in the process. Carbon dioxide is one of the waste molecules, and our bodies need to get rid of it as much as they need oxygen. If the blood level of carbon dioxide is high, it can lead to headaches, drowsiness, coma, and even death.
We inhale through our nose and mouth, and then air passes through the main windpipe called trachea, and continue through two bronchi to each lung. Air goes through smaller and smaller pipes until it reaches small sacks of air called alveoli. This structure of tubes in our lungs is often called a tracheobronchial tree because it is remarkably similar to the branching pattern of trees. Alveoli are surrounded by a fine network of tiny blood tubes called capillaries. This is where the exchange of gasses happen; oxygen enters blood where it is taken by red blood cells (erythrocytes) and later delivered further in the body. Erythrocytes also carry carbon dioxide to alveoli, where it is released, and then let out during the next expiration. Any breathing dysfunction can compromise this, and leave your body in a suboptimal state.
Hypoventilation during sleep is one of the sleep-related breathing disorders, and it involves slow or shallow breathing, known as respiratory depression. Usually, there is some problem in the communication between the brain, neurons, and the muscles, and it results in inappropriate breathing regulation. That can lead to a lack of oxygen and build up of carbon dioxide, which can even have fatal consequences.
Symptoms of Hypoventilation
This type of breathing disorder can occur in anyone, even babies and young children. The exact prevalence of this respiratory problem is not known, but it is not considered to be a common disorder. Because many different underlying conditions can be to blame for nocturnal hypoventilation, the symptoms vary between individuals. The most frequent ones include excessive daytime sleepiness, fragmentation of sleep, insomnia, morning headaches, stomach problems, difficulty breathing, faintness, mood changes, lack of focus, impaired memory, and reduced exercise capacity.
A lot of people don’t experience, or the symptoms are very mild in the beginning, so they don’t realize that they have a progressing condition. Chronic hypoventilation can lead to serious health problems such as respiratory and heart failure, and blood and brain disorders. Keep in mind that most of these signs also occur in other sleep-related disorders, so you need to check with a medical professional if you are experiencing any of them.
Causes of Hypoventilation
Many factors can lead to sleep hypoventilation syndrome. The autonomic nervous system that is in charge of involuntary movements like breathing may not work correctly, and it can lead to hypoventilation problem. Usage of specific medications such as opiates and benzodiazepines could also lead to this condition.
Obstructions of the airflow often caused by a medical condition such as emphysema, bronchitis and cystic fibrosis for the lower, and obstructive sleep apnea for the upper airway, are also risk factors. Nocturnal hypoventilation can also be due to a physical disorder such as an abnormally shaped chest wall, that is not letting lungs to move. People with muscular dystrophy are also more likely to suffer from this condition.
People with diseases of lung tissue are also more prone to hypoventilation. Smoking is a significant risk factor that causes inflammation and obstruction of the lower airway. Environmental factors, such as breathing in pollutants, chemicals, and other dangerous molecules can lead to damaging of the lungs and can cause a lack of respiration.
Neurological disorders where the brain’s control is impaired also leads to lack of respiration. Congenital central ventilation syndrome and central sleep apnea are good examples of that. Other medical conditions that could cause it are asthma and other pulmonary disorders, obesity, and hypothyroidism.
Different Types of Sleep-Related Hypoventilation Disorder
Within the term sleep-related hypoventilation, there are a few distinct disorders, that all have one thing in common, lack of gas exchange happening during sleep. Whether it is the cause of shallow or slow breathing, or a lung, brain or blood disorder, the body lacks oxygen and has excess carbon dioxide.
Hypoventilation can be caused by the excess weight that a person is carrying, and it is called obesity hypoventilation syndrome. Obesity is linked with many health problems, and all of the professionals agree that the goal for everybody would be to reach a healthy weight, as it greatly improves health, happiness, longevity and overall quality of life. Extra fat can block the airways, thus providing obstructions, and preventing the proper ventilation of the lungs.
Congenital hypoventilation syndrome appears in infants, and it is characterized by the abnormally slow and shallow breathing. Infants with this syndrome can appear bluish after or during sleep, and this condition is known as cyanosis (derived from the Greek kyanos meaning dark blue). Babies with this syndrome need an artificial diaphragm pacemaker to stimulate normal breathing patterns, and might also need mechanical ventilation. In most cases, that is only required during the night, but in more severe cases, they need this assistance all day long.
Central hypoventilation with hypothalamic dysfunction looks similar to congenital hypoventilation, but it appears later in childhood. Symptoms of this disorder are accompanied by signs of hypothyroidism, that include fatigue, feeling cold, and slow metabolism.
In some rare cases, the cause of the hypoventilation can be unknown, as everything looks normal upon observation. This condition is called primary alveolar hypoventilation.
Diagnosis and Treatment
A series of tests are done to determine if the patient is suffering from the sleep-related hypoventilation. Firstly, doctors will determine if the lungs are working correctly, then they’ll asses the respiratory muscle strength. Daytime oxygen and capillary gas tests are done to determine the quantity of oxygen and carbon dioxide in the blood during the day. All those tests can tell doctors if there is anything wrong with your respiration.
Additionally, they’ll need to do an overnight sleep study, called polysomnography. You’d have to stay in a sleep facility, where they hook you up to a bunch of electrodes and different machines that measure your brain waves, respiration, heart rate, oxygen blood levels, limbs, and chest movement, as well as any snoring or other sounds you might produce during sleep. The information gained from this study is essential, and it helps doctors to see what is exactly the cause of your nocturnal hypoventilation, and to treat it properly.
Treatment of sleep-related hypoventilation depends on the case, and it usually involves treating any underlying condition that might be the cause of it. For instance, for obese individuals, weight loss will be advised. For people with hypothyroidism, the regulation of hormone levels will be needed, while for people with a narrowed airway, respiratory stimulants might be prescribed. These substances help to correct the closed pipes that might be the consequences of drug or alcohol abuse.
For some other conditions, you might be prescribed oxygen or continuous positive airway pressure (CPAP) therapy. CPAP is mostly used as a treatment of sleep apnea, but it can be beneficial to other conditions as well. You usually put a mask over your nose or mouth, that is connected with a machine that sits next to your bed. The device is continuously pumping pressurized air so that you get the amount you need. There are different types of masks, and settings, so you can get the ones that suit you best, and you’d also need to follow your doctor’s instructions with the amount of air that is delivered to you.
Some people have problems with CPAP therapy as they have trouble breathing out with air continuously coming in. That’s why decide for a bilevel positive airway pressure (BiPAP) therapy. The principle behind this is similar to CPAP; it is just that there are two different pressures when you try to inhale and exhale. During inspiration, the pressure is stronger, filling you with the needed air, while it is weaker during expiration so that you don’t have any trouble doing it. These machines can also be programmed to take automatically take a breath if you haven’t inhaled for a certain amount of time, thus additionally preventing hypoventilation.